#tail{
    background-color: #202020;
    height: 220px;
    width: auto;

}
#end{
    background-color: black;
    height:105px;
    width: auto;
}
#tuijian{
    background: rosybrown;
    width: 65%;
    height: 0;
    padding-bottom: 30%;
    float: left;
    margin: auto;

}
#qiandao{
    background: turquoise;
    width: 35%;
    height: 0;
    padding-bottom: 30%;
    margin: auto;
    float: left;
}
#nav{
    height: 56px;
    width: 60%;
    background: crimson;
    margin: auto;
    
}
.nav_li{
    float: left;
}
.nav_a{
    display: block;
    color: #666;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
}
#nav_ul{
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    border: 1px solid #e7e7e7;
    background-color: #f3f3f3;
}
#main{
    height: auto;
    width: 60%;
    overflow:hidden;
    margin:auto;
}
.txt_end{
    margin: auto;
    color: white;

}